This is a FAQ. Please read perldoc -q unique. Specifically, you want "How can I extract just the unique elements of an array?" from Perl FAQ 4. This is also available online at http://www.perldoc.com/ if you don't have the docs installed on your computer (although you really should).

The reason you couldn't find it in the 5.6 docs is because they CHANGED THE ENTRY (Jeff says "grrrr" to that). It's now listed as "How can I remove duplicate elements from a list or array?". It's still in perlfaq4, though.